Kristen Stewart was attached to also star in the pic but when Smith became engaged in the project, Stewart fell off with the feeling that the age difference between the two would be too large a gap.

Smith had been weighing the film for some time and has committed to joining it.

Written and directed by Glenn Ficarra and John Requa, who helmed “Crazy, Stupid, Love” for the studio, the story follows an inexperienced female con artist who teams up with a more seasoned male one. Denise DiNovi will produce.

It’s a sign of positive forward movement for Warners, which has been trying to get the project made since Ficarra and Requa brought them the script early last year. The original idea was to reteam “Crazy Stupid Love” co-stars Ryan Gosling and Emma Stone for the leads, but when Gosling’s schedule could not be worked out, Warners began looking at other candidates.

Sources say the studio loves the script but knew it would be tough to greenlight without a top-tier actor, so it began courting leads such as Brad Pitt and Ben Affleck. Affleck came close but earlier commitments got in the way.

Smith has spent several months considering his next project. Though he has several sequels in development, it appears he was looking for something new and original.

Sources say he had considered making Hurricane Katrina pic “The American Can,” which he had been previously linked to, his next film, and that Warners had also approached him for “The Accountant.”

Smith, who can next be seen in Sony’s “After Earth,” is repped by CAA and Overbrook.